Mats Erik Andersson <mats.andersson@gisladisker.se> writes: > using packet dumps like "tcpdump -pnvXi bge0 ip" I have been > able to conclusively detect that kFreeBSD is inserting 0x0000 > as the IP header checksum in any TCP response triggered by an Are you using tcpdump to look at the checksums of outgoing packets? That's not going to work with checksum offloading. Can you run tcpdump on the receiver side instead? -Timo